1. Field of the Invention
The present invention relates to an organic EL display panel, an organic EL display device having the same, and a method for manufacturing an organic EL display panel.
2. Description of the Related Art
In recent years, research and development of organic EL display panels that use the phenomenon of electroluminescence occurring in organic material (hereinafter, simply “display panels”) have progressed. Each light-emitting cell of such a display panel has an anode, a cathode, and an organic light-emitting layer interposed between the anode and the cathode. When the display panel is driven, light is produced upon recombination of holes and electrons that are injected into the organic light-emitting layer through the anode and cathode, respectively.
Examples of methods for manufacturing such organic light-emitting layers include an evaporation method and a printing method. Especially when an ink-jet method, which is a type of printing method, is employed to form light-emitting layers and other layers, adjacent pixels need to be separated by banks (partitions) made from e.g., insulating material to avoid mixing of ink drops of different colors (color mixture). Schemes known for forming such banks include: a line-bank scheme according to which a plurality of banks are formed in parallel lines to separate organic light-emitting layers into stripes; and a pixel-bank scheme according to which banks are formed into a grid (lattice) pattern to enclose individual pixels with the banks.
With the line-bank scheme, when material for forming organic light-emitting layers is applied using a printing method such as an ink-jet method, the material flows across a plurality of light-emitting cells, so that the organic light-emitting layers in the respective light-emitting cells are ensured to be uniform in thickness. However, the line-bank scheme requires to additionally provide cell-defining layers traversing the banks arranged in lines. The cell-defining layers are provided to control emission of light at an edge portion of each light-emitting cell, so that the individual light-emitting cells aligned along the banks are separated. That is to say, a process of forming the cell-defining layers needs to be added to the entire process of forming organic EL elements, which gives a rise to a problem of increasing the manufacturing cost.
With the pixel-bank scheme, on the other hand, no additional layers such as the cell-defining layers mentioned above are necessary. Thus, the problem about the manufacturing cost is duly addressed. Yet, since the individual light-emitting cells are discretely separated, when material for forming organic light-emitting layers is applied using a printing method such as an ink jet method, the material cannot flow across a plurality of light-emitting cells. Thus, it is difficult to ensure that the organic light-emitting layers in the respective light-emitting cells are uniform in thickness.
Patent Literature 1 is one example showing a technique employing the line-bank scheme. According to Patent Literature 1, cell-defining layers made from insulating material are disposed between light-emitting cells adjacent in the direction in which the banks extend, so that interference of light emission between adjacent pixels is prevented. The cell-defining layers may be composed of the same material as the banks. The cell-defining layers composed of such material are referred to as “auxiliary banks (partitions)”. The cell-defining layers are formed to be lower in height than the line banks, so that ink is allowed to flow in the direction in which the banks extend. Consequently, the amount of ink is ensured to be uniform among a plurality of light-emitting cells.
3. Patent Literature    [Patent Literature 1]: JP Patent Application Publication No. 2009-200049